x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 242 insertions, 0 deletions

diff --git a/drivers/input/keyboard/amikbd.c b/drivers/input/keyboard/amikbd.c
new file mode 100644
index 000000000..ecfae0b0b
--- /dev/null
+++ b/drivers/input/keyboard/amikbd.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (c) 2000-2001 Vojtech Pavlik
+ *
+ *  Based on the work of:
+ *	Hamish Macdonald
+ */
+
+/*
+ * Amiga keyboard driver for Linux/m68k
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/keyboard.h>
+#include <linux/platform_device.h>
+
+#include <asm/amigaints.h>
+#include <asm/amigahw.h>
+#include <asm/irq.h>
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION("Amiga keyboard driver");
+MODULE_LICENSE("GPL");
+
+#ifdef CONFIG_VT
+static unsigned char amikbd_keycode[0x78] __initdata = {
+	[0]	 = KEY_GRAVE,
+	[1]	 = KEY_1,
+	[2]	 = KEY_2,
+	[3]	 = KEY_3,
+	[4]	 = KEY_4,
+	[5]	 = KEY_5,
+	[6]	 = KEY_6,
+	[7]	 = KEY_7,
+	[8]	 = KEY_8,
+	[9]	 = KEY_9,
+	[10]	 = KEY_0,
+	[11]	 = KEY_MINUS,
+	[12]	 = KEY_EQUAL,
+	[13]	 = KEY_BACKSLASH,
+	[15]	 = KEY_KP0,
+	[16]	 = KEY_Q,
+	[17]	 = KEY_W,
+	[18]	 = KEY_E,
+	[19]	 = KEY_R,
+	[20]	 = KEY_T,
+	[21]	 = KEY_Y,
+	[22]	 = KEY_U,
+	[23]	 = KEY_I,
+	[24]	 = KEY_O,
+	[25]	 = KEY_P,
+	[26]	 = KEY_LEFTBRACE,
+	[27]	 = KEY_RIGHTBRACE,
+	[29]	 = KEY_KP1,
+	[30]	 = KEY_KP2,
+	[31]	 = KEY_KP3,
+	[32]	 = KEY_A,
+	[33]	 = KEY_S,
+	[34]	 = KEY_D,
+	[35]	 = KEY_F,
+	[36]	 = KEY_G,
+	[37]	 = KEY_H,
+	[38]	 = KEY_J,
+	[39]	 = KEY_K,
+	[40]	 = KEY_L,
+	[41]	 = KEY_SEMICOLON,
+	[42]	 = KEY_APOSTROPHE,
+	[43]	 = KEY_BACKSLASH,
+	[45]	 = KEY_KP4,
+	[46]	 = KEY_KP5,
+	[47]	 = KEY_KP6,
+	[48]	 = KEY_102ND,
+	[49]	 = KEY_Z,
+	[50]	 = KEY_X,
+	[51]	 = KEY_C,
+	[52]	 = KEY_V,
+	[53]	 = KEY_B,
+	[54]	 = KEY_N,
+	[55]	 = KEY_M,
+	[56]	 = KEY_COMMA,
+	[57]	 = KEY_DOT,
+	[58]	 = KEY_SLASH,
+	[60]	 = KEY_KPDOT,
+	[61]	 = KEY_KP7,
+	[62]	 = KEY_KP8,
+	[63]	 = KEY_KP9,
+	[64]	 = KEY_SPACE,
+	[65]	 = KEY_BACKSPACE,
+	[66]	 = KEY_TAB,
+	[67]	 = KEY_KPENTER,
+	[68]	 = KEY_ENTER,
+	[69]	 = KEY_ESC,
+	[70]	 = KEY_DELETE,
+	[74]	 = KEY_KPMINUS,
+	[76]	 = KEY_UP,
+	[77]	 = KEY_DOWN,
+	[78]	 = KEY_RIGHT,
+	[79]	 = KEY_LEFT,
+	[80]	 = KEY_F1,
+	[81]	 = KEY_F2,
+	[82]	 = KEY_F3,
+	[83]	 = KEY_F4,
+	[84]	 = KEY_F5,
+	[85]	 = KEY_F6,
+	[86]	 = KEY_F7,
+	[87]	 = KEY_F8,
+	[88]	 = KEY_F9,
+	[89]	 = KEY_F10,
+	[90]	 = KEY_KPLEFTPAREN,
+	[91]	 = KEY_KPRIGHTPAREN,
+	[92]	 = KEY_KPSLASH,
+	[93]	 = KEY_KPASTERISK,
+	[94]	 = KEY_KPPLUS,
+	[95]	 = KEY_HELP,
+	[96]	 = KEY_LEFTSHIFT,
+	[97]	 = KEY_RIGHTSHIFT,
+	[98]	 = KEY_CAPSLOCK,
+	[99]	 = KEY_LEFTCTRL,
+	[100]	 = KEY_LEFTALT,
+	[101]	 = KEY_RIGHTALT,
+	[102]	 = KEY_LEFTMETA,
+	[103]	 = KEY_RIGHTMETA
+};
+
+static void __init amikbd_init_console_keymaps(void)
+{
+	/* We can spare 512 bytes on stack for temp_map in init path. */
+	unsigned short temp_map[NR_KEYS];
+	int i, j;
+
+	for (i = 0; i < MAX_NR_KEYMAPS; i++) {
+		if (!key_maps[i])
+			continue;
+		memset(temp_map, 0, sizeof(temp_map));
+		for (j = 0; j < 0x78; j++) {
+			if (!amikbd_keycode[j])
+				continue;
+			temp_map[j] = key_maps[i][amikbd_keycode[j]];
+		}
+		for (j = 0; j < NR_KEYS; j++) {
+			if (!temp_map[j])
+				temp_map[j] = 0xf200;
+		}
+		memcpy(key_maps[i], temp_map, sizeof(temp_map));
+	}
+}
+#else /* !CONFIG_VT */
+static inline void amikbd_init_console_keymaps(void) {}
+#endif /* !CONFIG_VT */
+
+static const char *amikbd_messages[8] = {
+	[0] = KERN_ALERT "amikbd: Ctrl-Amiga-Amiga reset warning!!\n",
+	[1] = KERN_WARNING "amikbd: keyboard lost sync\n",
+	[2] = KERN_WARNING "amikbd: keyboard buffer overflow\n",
+	[3] = KERN_WARNING "amikbd: keyboard controller failure\n",
+	[4] = KERN_ERR "amikbd: keyboard selftest failure\n",
+	[5] = KERN_INFO "amikbd: initiate power-up key stream\n",
+	[6] = KERN_INFO "amikbd: terminate power-up key stream\n",
+	[7] = KERN_WARNING "amikbd: keyboard interrupt\n"
+};
+
+static irqreturn_t amikbd_interrupt(int irq, void *data)
+{
+	struct input_dev *dev = data;
+	unsigned char scancode, down;
+
+	scancode = ~ciaa.sdr;		/* get and invert scancode (keyboard is active low) */
+	ciaa.cra |= 0x40;		/* switch SP pin to output for handshake */
+	udelay(85);			/* wait until 85 us have expired */
+	ciaa.cra &= ~0x40;		/* switch CIA serial port to input mode */
+
+	down = !(scancode & 1);		/* lowest bit is release bit */
+	scancode >>= 1;
+
+	if (scancode < 0x78) {		/* scancodes < 0x78 are keys */
+		if (scancode == 98) {	/* CapsLock is a toggle switch key on Amiga */
+			input_report_key(dev, scancode, 1);
+			input_report_key(dev, scancode, 0);
+		} else {
+			input_report_key(dev, scancode, down);
+		}
+
+		input_sync(dev);
+	} else				/* scancodes >= 0x78 are error codes */
+		printk(amikbd_messages[scancode - 0x78]);
+
+	return IRQ_HANDLED;
+}
+
+static int __init amikbd_probe(struct platform_device *pdev)
+{
+	struct input_dev *dev;
+	int i, err;
+
+	dev = devm_input_allocate_device(&pdev->dev);
+	if (!dev) {
+		dev_err(&pdev->dev, "Not enough memory for input device\n");
+		return -ENOMEM;
+	}
+
+	dev->name = pdev->name;
+	dev->phys = "amikbd/input0";
+	dev->id.bustype = BUS_AMIGA;
+	dev->id.vendor = 0x0001;
+	dev->id.product = 0x0001;
+	dev->id.version = 0x0100;
+
+	dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
+
+	for (i = 0; i < 0x78; i++)
+		set_bit(i, dev->keybit);
+
+	amikbd_init_console_keymaps();
+
+	ciaa.cra &= ~0x41;	 /* serial data in, turn off TA */
+	err = devm_request_irq(&pdev->dev, IRQ_AMIGA_CIAA_SP, amikbd_interrupt,
+			       0, "amikbd", dev);
+	if (err)
+		return err;
+
+	err = input_register_device(dev);
+	if (err)
+		return err;
+
+	platform_set_drvdata(pdev, dev);
+
+	return 0;
+}
+
+static struct platform_driver amikbd_driver = {
+	.driver   = {
+		.name	= "amiga-keyboard",
+	},
+};
+
+module_platform_driver_probe(amikbd_driver, amikbd_probe);
+
+MODULE_ALIAS("platform:amiga-keyboard");